Fox Glacier West Coast New Zealand
At 13 kilometres in length, Fox Glacier is the largest West Coast glacier. However, its current length pales in comparison to past size where in the last ice age the glacier extended almost to the sea leaving its tell-tale moraine walls as evidence of past advances, the most recent being in the 1750's.
Nearby Lake Matheson is a kettle lake formed by a decaying glacier as it retreated back to the existing valley. Since the 1950's the glacial retreat has been most marked although the occasional small advances have resulted in repeated realignment of the road and tracks nearby.
The glacier is feed by the vast snowfields that drain the southern alps at a height of approximately 2000 metres. The abundance of snowfall occurs as the moisture laden winds that sweep across the Tasman Ocean are forced upwards to flow over the mountains they have encountered. As they rise the air cools and the moisture is converted to rainfall.
Due to the steepness of the alps and their close proximity to the coast, this cooling becomes very rapid and hence the rainfall prolific!! Rainfall of 5840mm has been recorded close by to Haast township. At higher altitudes, this forms snow and during heavy snowfall years, the snow pack accumulates in these basins.
As the glacier obeys the laws of gravity the ice is slowly compacted and the river of ice continues to flow down the valley first formed thousands of years ago at the time of the first Ice Ages.
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As the leading edge of the ice pushes out, it collects boulders and debris in front of it, slowly pushing this down valley. When the melt rate exceeds the accumulation, the forward momentum slows and then stops. Without the forward momentum and in the face of higher melt rates, the glacier appears to retreat, leaving the wall of boulders and debris marking the further most point of progress. This wall is called the terminal moraine and evidence of past advances is clearly seen from the air.
At the same time the glacier is also pushing outwards forming similar walls along the edges. As the glacier shrinks lengthways, it will also shrink width wise again leaving moraine walls marking the sides of the glacier. These are termed the lateral moraines.
Glaciers will ebb and flow with the changing weather patterns of the world climates. At present the Fox Glacier is shrinking as the melt rate exceeds the accumulation in the upper snow fields. Perhaps in another 100 years this will have been reversed but until that time, we invite you to use Te Weheka as a base from where to grow your knowledge and understanding of glaciation.